Comparative Assessment of the Antibacterial Efficacies and Mechanisms of Different Tea Extracts.

Shuyuan Liu,Qiqi Zhang,Hang Li,Youben Yu,Zheyu Qiu

doi:10.3390/foods11040620

Shuyuan Liu, Qiqi Zhang + Show 3 more

Open Access

https://doi.org/10.3390/foods11040620

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Abstract

Tea is a popular beverage known for its unique taste and vast health benefits. The main components in tea change greatly during different processing methods, which makes teas capable of having different biological activities. We compared the antibacterial activity of four varieties of tea, including green, oolong, black, and Fuzhuan tea. All tea extracts showed antibacterial activity and Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus) were more susceptible to tea extracts than Gram-negative bacteria (Escherichia coli and Salmonella typhimurium). Green tea extracts inhibited bacterial pathogens much more effectively in all four varieties of tea with the minimum inhibitory concentration (MIC) values at 20 mg/mL, 10 mg/mL, 35 mg/mL, and 16 mg/mL for E. faecalis, S. aureus, E. coli, and S. typhimurium, respectively. Catechins should be considered as the main antibiotic components of the four tea extracts. Total catechins were extracted from green tea and evaluated their antibacterial activity. Additional studies showed that the catechins damaged the cell membrane and increased cell membrane permeability, leading to changes in the relative electrical conductivity and the release of certain components into the cytoplasm. Tea extracts, especially green tea extracts, should be considered as safe antibacterial food additives.

Highlights

Increased foodborne illness caused by foodborne spoilage and pathogenic bacteria has been a major food safety challenge and caused widespread concern [1]
Green tea extracts showed the highest antibacterial activity against both Gram-positive and Gramnegative bacteria, with the largest the diameter of the inhibition zone (DIZ) value at the same concentration of all four tea extracts, which was consistent with previous reports [22,41]
The minimum inhibitory concentration (MIC) values of the tea extracts against the test bacteria were consistent with the DIZ values (Table 2)

Summary

Introduction

Increased foodborne illness caused by foodborne spoilage and pathogenic bacteria has been a major food safety challenge and caused widespread concern [1]. Pathogenic bacteria have been reported to pose serious threats to human health, such as causing food poisoning, toxic shock syndrome, and infections [2]. The chemical preservatives used in food have been reported causing respiratory illnesses or other health risks [3]. There is a need to develop novel types of effective plant-derived antimicrobial compounds with safety, biodegradability, and fewer side effects [4]. Some plant extracts, including tea leaves (Camellia sinensis (L.) O. Kuntze), have been reported to display good inhibitory effects against pathogenic bacteria and may support the development of antimicrobial supplements [5,6]

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